Semiconductor device and method of manufacturing the same

ABSTRACT

Provided is a semiconductor device including a semiconductor substrate having transistors formed thereon, a first interlayer insulating film formed above the semiconductor substrate and the transistors, a ferroelectric capacitor formed above the first interlayer insulating film, a second interlayer insulating film formed above the first interlayer insulating film and the ferroelectric capacitor, a first metal wiring formed on the second interlayer insulating film, and a protection film formed on an upper surface of the wiring but not on a side surface of the wiring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon prior International Patent ApplicationNo. PCT/JP2007/071419, filed on Nov. 2, 2007, the entire contents ofwhich are incorporated herein by reference.

FIELD

It is related to a semiconductor device and a method of manufacturingthe same.

BACKGROUND

In recent years, ferroelectric random access memories (FeRAMs) aredeveloped in which information is stored in ferroelectric capacitors byusing polarization inversion of a ferroelectric material. FeRAMs arenonvolatile memory which do not lose information stored therein, even ifbeing turned off, and can achieve high integration degree, high-speeddrive, high durability, low power consumption and the like. Due to theseadvantages, attentions are given especially to FeRAMs.

A related art is disclosed in Japanese Laid-open Patent publication Nos.2005-183842 and 2006-202848

In Japanese Laid-open Patent publication No. 2006-202848, a capacitor isenveloped by an alumina film (paragraph No. 0030).

SUMMARY

According to one aspect discussed herein, there is provided asemiconductor device including a semiconductor substrate including atransistor, a first interlayer insulating film formed over thesemiconductor substrate and the transistor, a ferroelectric capacitorformed over the first interlayer insulating film, a second interlayerinsulating film formed over the first interlayer insulating film and theferroelectric capacitor, a wiring formed over the second interlayerinsulating film, and a protection film formed over an upper surface ofthe wiring but not on a side surface of the wiring.

According to another aspect discussed herein, there is provided a methodof manufacturing a semiconductor device, including forming a transistoron a semiconductor substrate, forming a first interlayer insulating filmover the semiconductor substrate and the transistor, forming aferroelectric capacitor over the first interlayer insulating film,forming a second interlayer insulating film over the first interlayerinsulating film and the ferroelectric capacitor, forming a wiring overthe second interlayer insulating film, and forming a protection filmover an upper surface of the wiring but not on a side surface of thewiring.

Other Objects and further features of the present application willbecome apparent from the following detailed description when read inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1G are cross-sectional views of an investigated FeRAM in thecourse of manufacturing;

FIGS. 2A to 2Z and 3A to 3E are cross-sectional views of a semiconductordevice according to a first embodiment in the course of manufacturing;

FIG. 4 is a graph depicting results of an investigation on residualpolarization charges in capacitor dielectric films;

FIG. 5 is a configuration diagram of a plasma chemical vapor deposition(CVD) apparatus employed in the first embodiment and a secondembodiment; and

FIGS. 6A to 6V are cross-sectional views of a semiconductor deviceaccording to the second embodiment in the course of manufacturing.

DESCRIPTION OF EMBODIMENTS

Before providing description of embodiments, results of an investigationcarried out by the inventor of the present application are described.

In the course of manufacturing a FeRAM, a capacitor dielectric film madeof a ferroelectric oxide is damaged by various factors.

For example, in the step of depositing an interlayer insulating filmmade of silicone oxide over the capacitor dielectric film, the capacitordielectric film is reduced by reducing substances such as hydrogencontained in a deposition atmosphere, and is thereby deteriorated.

In addition, from experience of the inventor of the present application,it is also known that plasma damage occurs in the capacitor dielectricfilm, when the interlayer insulating film is formed by a plasma chemicalvapor deposition (CVD) method. It is empirically revealed that suchplasma damage prominently occurs when a wiring electrically connected toan upper electrode is exposed to plasma. Moreover, plasma damage occursin the capacitor dielectric film also when the upper electrode or thecapacitor dielectric film is exposed to a plasma atmosphere.

Such deterioration of the capacitor dielectric film attributable to thereducing substances or plasma damage is considered to be prevented if aninsulating hydrogen barrier film is formed on the wirings.

In the following, description is given of a FeRAM including such aninsulating hydrogen barrier film.

FIGS. 1A to 1G are cross-sectional views of a FeRAM in the course ofmanufacturing used in the investigation by the inventor of the presentapplication.

Firstly, steps for obtaining a cross-sectional structure illustrated inFIG. 1A are described.

First, by a local oxidation of silicon (LOCOS) method, an elementisolation insulating film is formed on a silicon substrate 1. Then, ametal oxide semiconductor (MOS) transistor TR is formed in each activeregion of the silicon substrate 1 defined by the element isolationinsulating film 11.

Thereafter, a cover insulating film 12 made of silicon nitride (SiN) anda base insulating film 13 made of silicon oxide (SiO₂) are formed overthe entire upper surface of the silicon substrate 1 by a plasma CVDmethod.

Moreover, a ferroelectric capacitor Q is formed on the base insulatingfilm 13. The capacitor Q is formed by laminating a lower electrode 15made of platinum, a capacitor dielectric film 16 made of PZT and anupper electrode 17 made of iridium oxide (IrO₂), in this order from thebottom.

Subsequently, the capacitor Q is covered by a first insulating hydrogenbarrier film 18 made of alumina, to protect the capacitor dielectricfilm 16 from a reducing material.

After forming the first interlayer insulating film 19 made of siliconoxide on the first insulating hydrogen barrier film 18, the firstinterlayer insulating film 19 is patterned by a photolithography, andthereby first to third holes 19 a to 19 c are formed as illustrated inFIG. 1A.

Thereafter, a conductive plug 20 mainly made of tungsten is embedded inthe third hole 19 c reaching the transistor TR.

Next, as illustrated in FIG. 1B, a metal laminated film 21 mainly madeof an aluminum film is formed in the first and the second holes 19 a and19 b and on the interlayer insulating film 19.

Moreover, a photoresist is applied to the metal laminated film 21, andis then exposed and developed. Thereby, a resist pattern 22 is formed.

Subsequently, as illustrated in FIG. 1C, the metal laminated film 21 ispatterned by using the resist pattern 22 as a mask, and thereby wirings23 are formed.

Then, as illustrated in FIG. 1D, the resist pattern 23 is removed byasking, and then a resist residue is removed by a wet process usingchemical liquid and pure water.

By this wet process, the wirings 23 absorb moisture. In addition,impurities attributable to a resist such as hydrocarbon may be attachedto the surfaces of the wirings 23, since it is difficult to completelyremove the resist residue by the wet process.

If moisture and hydrocarbon are attached to the wirings 23 in thismanner, a film to be formed on the wirings 23 may peel off from thewirings 23.

To deal with this problem, as illustrated in FIG. 1E, in the next step,annealing is performed on the wirings 23 in a nitrogen atmosphere.Thereby, impurities such as moisture and hydrocarbon attached to thewirings 23 evaporate, and thus the surfaces of the wirings 23 arecleaned. This annealing is performed under the conditions of, forexample, a substrate temperature of 350° C., a nitrogen flow rate of 20liter/min, and a process time of 30 minutes.

Subsequently, as illustrated in FIG. 1F, an alumina film is formed as asecond insulating hydrogen barrier film 25 on the wirings 23 and thefirst interlayer insulating film 19 by a sputtering method.

Since the impurities are vaporized by the annealing performed on thewirings 23 in the step illustrated in FIG. 1E, excellent adhesiveness isobtained between the second insulating hydrogen barrier film 25 and thewirings 23.

Then, as illustrated in FIG. 1G, a silicon oxide film to serve as asecond interlayer insulating film 26 is formed on the second insulatinghydrogen barrier film 25 by a plasma CVD method using tetraethoxysilane(TEOS) gas. Since a deposition temperature can be lowered in a plasmaCVD method than in a low-pressure CVD method or the like, the plasma CVDmethod is advantageous in that the capacitor dielectric film 16 is lesslikely to deteriorate due to heat.

When depositing the second interlayer insulating film 26, the wirings 23are covered with the second insulating hydrogen barrier film 25, and arehence not directly exposed to a plasma atmosphere used in depositing thesecond interlayer insulating film 26. Accordingly, plasma damage to thecapacitor dielectric film 16 can be reduced in the capacitor Qelectrically connected to the wirings 23.

Subsequently, an upper surface of the second interlayer insulating film26 is polished by a chemical mechanical polishing (CMP) method. In thisway, a basic structure of the FeRAM used in this investigation iscompleted.

In the above-described method of manufacturing a FeRAM, the secondinsulating hydrogen barrier film 25 is formed to cover the wirings 23,and consequently the wirings 23 are isolated from the plasma atmosphereused when depositing the second interlayer insulating film 26. Thereby,plasma damage caused on the capacitor dielectric film 16 through thewirings 23 is intended to be prevented.

However, this method requires annealing as described by using FIG. 1E,in order to prevent the second insulating hydrogen barrier film 25 frompeeling off from the wirings 23. This causes another problem that thecapacitor dielectric film is deteriorated by heat if such annealing isperformed after the capacitor Q is formed. The investigation carried outby the inventor of the present application reveals that the residualpolarization charge of the capacitor dielectric film 16 decreases byapproximately 3% to 8% in the case of performing such annealing comparedwith the case of not performing the annealing.

In addition, if water is remaining on the first interlayer insulatingfilm 19, the capacitor Q is steamed during the annealing, which causesfurther deterioration of the capacitor dielectric film 16. This problemof steaming is prominent especially when the alumina film is formed at amid-depth of the first interlayer insulating film 19 to effectivelyprevent hydrogen in an external atmosphere from reaching the capacitorQ.

It is also conceivable to compensate oxygen deficiency of the capacitordielectric film 16 by annealing the capacitor dielectric film 16 at ahigh temperature in an oxygen-containing atmosphere after the wirings 23are formed, in order to restore the residual polarization charge.However, if such annealing is performed, the conductive plug 20 mainlymade of tungsten, which is easily oxidized, and the wirings 23 areoxidized. This causes another problem that contact resistance betweenthe conductive plug 20 and the wirings 23 increases.

The inventor of the present application has reached the embodiments tobe described below, in order to solve these newly-found problems.

First Embodiment

Firstly, description is given of a semiconductor device according to afirst embodiment on the basis its manufacturing steps.

FIGS. 2A to 2Z and 3A to 3E are cross-sectional views of thesemiconductor device according to this embodiment in the course ofmanufacturing. Note that, in these drawings, a peripheral circuit regionR_(peripheral), a logic circuit region R_(logic), a cell region R_(cell)and a pad region R_(pad) of a single semiconductor chip are illustrated.

This semiconductor device is a planar-type FeRAM, and is manufactured asfollows.

Firstly, description is given of steps for obtaining a cross-sectionstructure illustrated in FIG. 2A.

First, an element isolation insulating film 31 is formed by thermallyoxidizing a surface of an n-type or p-type silicon (semiconductor)substrate 30, and active regions for transistors are defined by theelement isolation insulating film 31. The element isolation insulatingfilm 31 has a film thickness of, for example, approximately 200 nm whenmeasured from the upper surface of the silicon substrate 30. Instead ofsuch an element isolation technique using LOCOS, shallow trenchisolation (STI) may be used.

Then, first and second p-wells 32 and 33 are formed by implanting ionsof a p-type impurity, for example, boron, into active regions of thesilicon substrate 30, and a surface of each active region is thermallyoxidized. Thereby, a thermal oxide film to serve as a gate insulatingfilm 34 is formed to have a thickness of approximately 6 nm to 7 nm.

Subsequently, an amorphous silicon film having a thickness ofapproximately 50 nm and a tungsten silicide film having a thickness ofapproximately 150 nm are formed in this order over the entire uppersurface of the silicon substrate 30. Here, a polycrystalline siliconfilm may be formed instead of the amorphous silicon film. Then, bypatterning these films by photolithography, gate electrodes 35 areformed in the logic circuit region R_(logic) and the cell regionR_(cell) of the silicon substrate 30, whereas a wiring 36 is formed inthe peripheral circuit region R_(peripheral) of the element isolationinsulating film 31.

The gate length of each gate electrode 35 is approximately 360 μm, forexample.

Next, by ion implantation using the gate electrodes 35 as masks,phosphorus is implanted as an n-type impurity into the silicon substrate30 beside the gate electrodes 35. Thereby, first to third source/drainextensions 37 a to 37 c are formed.

Thereafter, an insulating film is formed over the entire upper surfaceof the silicon substrate 30, and the insulating film is etched back sothat the insulting film is left as insulating side walls 38 on the sidesurfaces of the gate electrodes 35 and the wiring 36. As the insulatingfilm, a silicon oxide film is formed to a thickness of 45 nm by a CVDmethod, for example.

Then, ions of an n-type impurity such as arsenic are implanted into thesilicon substrate 30 while using the insulating side walls 38 and thegate electrodes 35 as masks. Thereby, first to third source/drainregions 39 a to 39 c are formed in the silicon substrate 30 beside thegate electrodes 35.

Further, a refractory metal film such as a cobalt film is formed on theentire upper surface of the silicon substrate 30 by a sputtering method.Then, by heating the refractory metal film to cause the refractory metalfilm to react with silicon, a refractory silicide layer 41 such as acobalt silicide layer is formed on the first to third source/drainregions 39 a to 39 c of the silicon substrate 30. In this way, theresistance of each of the source/drain regions 39 a to 39 c is reduced.The refractory metal silicide layer is also formed on surfaces of thegate electrodes 35 and the wiring 36.

Thereafter, unreacted portions of the refractory metal layer on theelement isolation insulating film 31 and the like are removed by wetetching.

Through the above-described steps, first to third MOS transistors TR₁ toTR₃ are formed in the cell region R_(cell) and the logic regionR_(logic) of the silicon substrate 30. The first to third MOStransistors TR₁ to TR₃ are each formed of the gate insulating film 34,the gate electrode 35, and the first to third source/drain regions 39 ato 39 c and the like.

Next, as illustrated in FIG. 2B, a silicon oxynitride (SiON) film toserve as a base insulating film 44 is formed on the entire upper surfaceof the silicon substrate 30 by a plasma CVD method to have a thicknessof approximately 200 nm.

Moreover, a silicon oxide film to serve as a first interlayer insulatingfilm 45 is formed on the base insulating film 44 by a plasma CVD methodusing a mixed gas of TEOS gas and oxygen gas, to have a thickness ofapproximately 600 nm. Thereafter, to planarize an upper surface of thefirst interlayer insulating film 45, the upper surface is polished by aCMP method. The amount to be polished is approximately 200 nm, forexample.

Thereafter, as illustrated in FIG. 2C, a silicon oxide film to serve asa first cap insulating film 46 is formed on the first interlayerinsulating film 45 by a plasma CVD method using TEOS gas, to have athickness of approximately 100 nm.

Then, as a dehydration process for the insulating films 45 and 46,annealing is performed at a substrate temperature of approximately 650°C. in a nitrogen atmosphere for approximately 30 minutes, and then analumina film 40 is formed on the first cap insulating film 26 by asputtering method to have a thickness of approximately 20 nm.

Subsequently, rapid thermal annealing (RTA) is performed on the aluminafilm 40 at a substrate temperature of 650° C. in an oxygen atmospherefor a process time of 60 seconds.

By forming the first cap insulating film 46 in advance before formingthe alumina film 40 in this manner, micro scratches made in the uppersurface of the first interlayer insulating film 45 due to contact with apolishing pad in the CMP are filled with the first cap insulating film46. Thereby, the alumina film 40 is formed to be flat on the uppersurface of the first cap insulating film 46.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2D.

First, a platinum film is formed as a first conductive film 47 on thealumina film 40 by a sputtering method. The first conductive film 47 islater patterned to serve as a capacitor lower electrode having a filmthickness of approximately 155 nm.

Moreover, a PZT film to serve as a ferroelectric film 48 is formed onthe first conductive film 47 by a sputtering method to have a thicknessof 150 nm to 200 nm.

As a method of depositing the ferroelectric film 48, a metal organic CVD(MOCVD) method or a sol-gel method may be employed instead of asputtering method. In addition, the material of the ferroelectric film48 is not limited to PZT, and the ferroelectric film 48 may be made of:a bismuth layer structured compound such as SBT(SrBi₂Ta₂O₉), SrBi₂(Ta_(x)Nb_(1-x))₂O₉ or Bi₄Ti₂O₁₂; PLZT(Pb_(1-x)La_(x)Zr_(1-y)Ti_(y)O₃)which is PZT doped with lanthanum; or other metal oxide ferroelectric.

Here, the PZT formed by the sputtering method is mostly not crystallizedimmediately after the deposition, and hence has poor dielectriccharacteristics. In view of this, as crystallization annealing forcrystallizing the PZT forming the ferroelectric film 48, RTA isperformed at a substrate temperature of approximately 585° C. in anoxygen-containing atmosphere having a oxygen flow rate of 0.025liter/min, for approximately 90 seconds. Note that such crystallizationannealing is not required when the ferroelectric film 48 is formed by aMOCVD method.

Next, a first iridium oxide film is formed on the ferroelectric film 48by a sputtering method to have a thickness of approximately 50 nm, andthen RTA is performed on the first iridium oxide film. Conditions forthe RTA are not particularly limited. In this embodiment, the RTA isperformed at a substrate temperature of 725° C. in an oxygen-containingatmosphere having an oxygen flow rate of 0.025 liter/min, for a processtime of 20 seconds.

Subsequently, a second iridium oxide film is formed on the first iridiumoxide film by a sputtering method to have a thickness of approximately200 nm. The stacked film of the first and second iridium oxide filmsserves as a second conductive film 49.

Here, forming the first conductive film 47 on the alumina film 40provides excellent orientation of platinum constituting the firstconductive film 47, compared with the case in which the first conductivefilm 47 is formed directly on the first cap insulating film 46 withoutforming the alumina film 40. Due to the action of the orientation of thefirst conductive film 47, the orientations of the PZT constituting theferroelectric film 48 are aligned, and hence the ferroelectric film 48has improved ferroelectric characteristics.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2E.

First, the second conductive film 49 is patterned by photolithography toform an upper electrode 49 a. Then, to recover damage caused to theferroelectric film 48 by the patterning, recovery annealing is performedon the ferroelectric film 48 in a vertical furnace. This recoveryannealing is performed in an oxygen-containing atmosphere having anoxygen flow rate of 20 liter/min under the conditions of a substratetemperature of 650° C. and a process time of 60 minutes, for example.

Thereafter, the ferroelectric film 48 is patterned by photolithographyto form a capacitor dielectric film 48 a made of a ferroelectricmaterial such as PZT. Damage caused to the capacitor dielectric film 48a by the patterning is recovered by recovery annealing. This recoveryannealing is performed in an oxygen-containing atmosphere in a verticalfurnace under the conditions of an oxygen flow rate of 20 liter/min, asubstrate temperature of 350° C. and a process time of 60 minutes.

Subsequently, as illustrated in FIG. 2F, an alumina film is formed overthe entire upper surface of the silicon substrate 30 by a sputteringmethod to have a thickness of approximately 50 nm, as a first insulatinghydrogen barrier film 51 for protecting the capacitor dielectric film 48a from reducing substances such as hydrogen and moisture.

Here, instead of the alumina film, any one of a titanium oxide (TiO_(x))film, a zirconium oxide (ZrO_(x)) film, a magnesium oxide (MgO) film anda titanium magnesium oxide (MgTiO_(x)) film may be formed as the firstinsulating hydrogen barrier film 51.

Then, to recover damage caused to the capacitor dielectric film 28 a bythe sputtering, recovery annealing is performed at a substratetemperature of 550° C. in an oxygen-containing atmosphere having anoxygen flow rate of 20 liter/min, for approximately 60 minutes. Thisrecovery annealing is performed in a vertical furnace.

Subsequently, as illustrated in FIG. 2G, the first conductive film 47and the first insulating hydrogen barrier film 51 are patterned byphotolithography. By this patterning, a portion of the first conductivefilm 47 under the capacitor dielectric film 48 a is made into a lowerelectrode 47 a, and the first insulating hydrogen barrier film 51 isleft so as to cover the lower electrode 47 a.

In this patterning, portions of the alumina film 40 that are not coveredby the lower electrode 47 a are also removed.

Thereafter, to recover damage caused to the capacitor dielectric film 48a during the process, recovery annealing is performed on the capacitordielectric film 48 a in an oxygen-containing atmosphere having an oxygenflow rate of 20 liter/min under the conditions of a substratetemperature of 650° C. and a process time of 60 minutes. This recoveryannealing is performed in a vertical furnace, for example.

Through the above-described steps, a capacitor Q including the lowerelectrode 47 a, the capacitor dielectric film 48 a and the upperelectrode 49 a deposited in this order is formed on the first interlayerinsulating film 45. Although multiple capacitors Q are formed in thecell region R_(cell), only a single capacitor Q is illustrated in thisembodiment for the sake of simplicity.

Subsequently, as illustrated in FIG. 2H, an alumina film is formed overthe entire upper surface of the silicon substrate 30 by a sputteringmethod to have a thickness of approximately 20 nm, as a secondinsulating hydrogen barrier film 53 for protecting the capacitor Q. Thesecond insulating hydrogen barrier film 53 together with the firstinsulating hydrogen barrier film 51 provided thereunder functions toprevent reducing substances such as hydrogen and moisture from reachingthe capacitor dielectric film 48 a and to thereby prevent deteriorationof the ferroelectric characteristics of the capacitor dielectric film 48a attributable to reduction of the capacitor dielectric film 48 a.

Films having such a function include a titanium oxide film, a zirconiumoxide film, a magnesium oxide film and a titanium magnesium film inaddition to an alumina film, and any one of these films may be formed asthe second insulating hydrogen barrier film 53.

Then, recovery annealing is performed on the capacitor dielectric film48 a in an oxygen-containing atmosphere in a vertical furnace under theconditions of a substrate temperature of 550° C. and a process time of60 minutes. The oxygen flow rate in this recovery annealing is 20liter/min, for example.

Subsequently, as illustrated in FIG. 2I, a silicon oxide film to serveas a second interlayer insulating film 55 is formed on the secondinsulating hydrogen barrier film 53 by a plasma CVD method using TEOSgas, to have a thickness of approximately 1500 nm.

Thereafter, as a dehydration process for the second interlayerinsulating film 55, a N₂O plasma process using a CVD apparatus isperformed. For this process, the substrate temperature is set at 350°C., and the process time is set at two minutes.

This N₂O plasma process dehydrates the second interlayer insulating film55 and prevents moisture resorption of the second interlayer insulatingfilm 55 by nitriding an upper surface of the second interlayerinsulating film 55.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2J.

First, a photoresist is applied onto the second interlayer insulatingfilm 55, and is then exposed and developed. Thereby, a first resistpattern 57 including hole-shaped first windows 57 a is formed.

Then, the insulating films from the second interlayer insulating film 55to the base insulating film 44 are dry-etched by using the first resistpattern 57 as a mask. Thereby, a first hole 58 a is formed in thesefilms under each of the first windows.

This dry etching is performed in a parallel-plate type plasma etchingapparatus (not illustrated). As an etching gas used for the first andsecond interlayer insulating films 45 and 55 and the first capinsulating film 46, which are made of silicon oxide, a gas mixture ofC₄F₈,O₂,Ar is used. In some cases, CO gas may be added to the etchinggas. Additionally, the second insulating hydrogen barrier film 53, madeof alumina, is also etched by the sputtering action of this etching gas.

In contrast, as an etching gas for the base insulating film 44 made ofsilicon oxy-nitride, a gas mixture of CHF₃, O₂, and Ar is used.

When this etching is completed, the first resist pattern 57 is removed.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2K.

First, a titanium (Ti) film and a titanium nitride (TiN) film to serveas a glue film are formed on an inner surface of each of the first holes58 a and the upper surface of the second interlayer insulating film 55by a sputtering method to have a thickness of 20 nm and a thickness of50 nm, respectively. Then, a tungsten film is formed on the glue film bya CVD method using tungsten hexafluoride gas, to have a thickness of 500nm. Thereby, the first holes 58 a are completely filled with thetungsten film.

Thereafter, excess glue film and the tungsten film on the secondinterlayer insulating film 55 is removed by polishing by a CMP method,and the glue film and the tungsten film are left in the first holes 58 aas first conductive plugs 60.

Among the conductive plugs 60, those formed in the cell region R_(cell)are each electrically connected to the corresponding one of the firstand second source/drain regions 39 a and 39 b. On the other hand, thefirst conductive plugs 60 formed in the logic circuit region R_(logic)are each electrically connected to the corresponding one of the thirdsource/drain regions 39 c. Then, the first conductive plug 60 formed inthe peripheral circuit region R_(peripheral) is electrically connectedto the wiring 36.

An N₂O plasma process using a CVD apparatus may be performed on thesecond interlayer insulating film 55 after the formation of the firstconductive plugs 60, for dehydration and prevention of moistureresorption of the second interlayer insulating film 55. The dehydrationprocess is performed under the conditions of a substrate temperature of350° C. and a process time of two minutes, for example.

The first conductive plugs 60 are mainly made of tungsten, which isextremely easily oxidized. Accordingly, the first conductive plugs 60may easily be oxidized in an oxygen-containing atmosphere and causecontact failure.

To deal with this problem, in the next step, as illustrated in FIG. 2L,a silicon oxy-nitride film to serve as an oxidation-preventioninsulating film 61 is formed on upper surfaces of the conductive plugs60 and the second interlayer insulating film 55 by a CVD method to havea thickness of approximately 100 nm, in order to prevent the firstconductive plugs 60 from being oxidized.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2M.

First, a photoresist is applied onto the oxidation-prevention insulatingfilm 61, and is then exposed and developed. Thereby, a second resistpattern 63 is formed. As illustrated in FIG. 2M, hole-shaped second andthird windows 63 a and 63 b are formed respectively at portions, overthe upper electrode 49 a and the lower electrode 47 a, of the secondresist pattern 63.

Thereafter, a second hole 55 a and a third hole 55 b are formedrespectively over the upper electrode 49 a and a contact region of thelower electrode 47 a, by etching the oxidation-prevention insulatingfilm 61, the second interlayer insulating film 55 and the first andsecond insulating hydrogen barrier films 51 and 53 by using the secondresist pattern 63 as a mask.

After the second resist pattern 63 is removed, the silicon substrate 30is put into a vertical furnace having an oxygen-containing atmosphere,and recovery annealing is performed on the capacitor dielectric film 48under the conditions of a substrate temperature of 500° C. and a processtime of 60 minutes to recover damage caused to the capacitor dielectricfilm 48 a in the above-described steps. For this annealing, the oxygenflow rate is set at 20 liter/min, for example.

Subsequently, the oxidation-prevention insulating film 61 is removed byetch back.

Next, as illustrated in FIG. 2N, a metal laminated film (conductivefilm) 65 is formed on upper surfaces of the second interlayer insulatingfilm 55 and the first conductive plugs 60 and inner surfaces of thesecond and third holes 55 a and 55 b by a sputtering method. In thisembodiment, as the metal laminated film 65, a titanium nitride filmhaving a thickness of approximately 150 nm, a copper-containing aluminumfilm having a thickness of approximately 550 nm, a titanium film havinga thickness of approximately 5 nm and a titanium nitride film having athickness of approximately 150 nm are formed in this order.

The metal laminated film 65 immediately after deposition adsorbs littleimpurities such as moisture and hydrocarbon on its surface. For thisreason, a film can be formed on the metal laminated film 65 immediatelyafter the formation of the metal laminated film 65 without performing,on the metal laminated film 65, annealing such as that performed afterremoval of a resist to vapor such impurities. By skipping suchannealing, deterioration of the capacitor dielectric film 48 a due toheat can be prevented.

Next, as illustrated in FIG. 2O, an alumina film to serve as aprotection film 64 is formed by a sputtering method to have a thicknessof approximately 20 nm.

The protection film 64 functions as a plasma protection film whichprevents the metal laminated film 65 from being directly exposed to aplasma atmosphere used in forming a third interlayer insulating film tobe described later, and prevents deterioration of the capacitor Qconnected to the metal laminated film 65 by plasma.

Accordingly, it is preferable to employ, as a method of depositing theprotection film 64, a method not using a plasma atmosphere as adeposition atmosphere, so as to prevent deterioration of the capacitor Qin depositing the protection film 64.

Although a sputtering method uses a plasma atmosphere as a depositionatmosphere, plasma is attracted to a sputtering target facing asubstrate and is not attracted to the substrate. Accordingly, even ifthe protection film 64 is formed by a sputtering method, little damageis caused to the capacitor Q.

The protection film 64 may alternatively be formed of an insulatingmetal oxide film other than an alumina film. Examples of such aninsulating metal oxide film other than an alumina film include atitanium oxide film, a zirconium oxide film, a magnesium oxide film, anda titanium magnesium oxide film. These insulating metal oxide films alsofunction as a hydrogen diffusion prevention film for preventing hydrogencontained in an external atmosphere from reaching the capacitordielectric film 48 a.

Moreover, as described above, since impurities such as moisture andhydrocarbon is not adhered to the surface of the metal laminated filmbefore the protection film 64 is formed, it is possible to prevent thepeel off of the protection film 64 from the metal laminated film 65attributable to the impurities, and to obtain excellent adhesivenessbetween the films.

Subsequently, as illustrated in FIG. 2P, a photoresist is applied ontothe protection film 64, and is then exposed and developed. Thereby, athird resist pattern 62 is formed.

Then, as illustrated in FIG. 2Q, the protection film 64 and the metallaminated film 65 are dry-etched by using the third resist pattern 62 asa mask. Thereby, the metal laminated film 65 is made into first metalwirings 65 a.

The dry etching for the protection film 64 is performed in aparallel-plate type etching apparatus by using a gas mixture of C₄F₈,Ar, and O₂ as an etching gas. In this case, the flow rates of C₄F₈ gas,Ar gas and O₂ gas are set at 20 sccm, 500 sccm and 12 sccm,respectively, for example. Additionally, CF₄, CHF₃ or CO may be added tothese gases.

In contrast, the dry etching for the metal laminated film 65 isperformed by using a gas mixture of BCl₃ and Cl₂ as an etching gas. Theflow rates of BCl₃ gas and Cl₂ gas are set at 105 sccm and 45 sccm,respectively, for example.

The second interlayer insulating film 55 made of silicon oxide is hardlyetched by the etching gas, and therefore functions as a stopper of theetching.

Here, among the first metal wirings 65 a, those formed on the capacitorQ are electrically connected to the upper electrode 49 a and the lowerelectrode 47 a through the first and second holes 55 a and 55 b,respectively.

Thereafter, the third resist pattern 62 is removed by ashing.

Here, after the ashing, a residue of the third resist pattern 62 may beremoved by a wet process using chemicals and pure water.

Even if the wet process is performed, a decrease in adhesiveness betweenthe protection film and the first metal wirings 65 a due to water orhydrocarbon generated by the wet process does not occur, since theprotection film 64 is already formed on the first metal wrings 65 a.

Accordingly, it is not necessary to perform, on the first metal wirings65 a, annealing to improve adhesiveness with the protection film 64 byvaporizing water and hydrocarbon. By skipping such annealing,deterioration of the capacitor dielectric film 48 a due to heat duringthe annealing can be prevented in this embodiment.

Then, as illustrated in FIG. 2R, an alumina film to serve as a thirdinsulating hydrogen barrier film 66 for covering the first metal wirings65 a and the second interlayer insulating film 55 is formed by asputtering method to have a thickness between 5 nm and 30 nm, e.g., 20nm.

The third insulating hydrogen barrier film has a function of blockingreducing substances such as hydrogen and moisture and thereby protectingthe capacitor dielectric film 48 a. Examples of a film having such afunction other than an alumina film include a titanium oxide film, azirconium oxide film, a magnesium oxide film and a titanium magnesiumfilm, and any one of the films may be formed as the third insulatinghydrogen barrier film 66.

To maintain sufficient barrier properties against reducing substances,it is preferable to form the third insulating hydrogen barrier film 66having a thickness of 5 nm or thicker.

Alternatively, a silicon-containing insulating film containing nitrogensuch as a silicon nitride (SiN) film or a silicon oxy-nitride (SiON)film may be formed as the third insulating hydrogen barrier film 66.Although falling behind an insulating metal oxide film, suchsilicon-containing insulating films have practically sufficient barrierproperties against hydrogen.

Among these silicon-containing insulating films, the silicon nitridefilm has more excellent barrier properties against hydrogen than thesilicon oxy-nitride film, and is hence preferable as the thirdinsulating hydrogen barrier film 66.

If deterioration of the capacitor dielectric film 48 a due to hydrogenis not an issue, the third insulating hydrogen barrier film 66 may beomitted.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2S.

FIG. 5 is a configuration diagram of a plasma CVD apparatus employed inthe step.

A plasma CVD apparatus 200 includes a chamber 201, in which a waferstage 202 for holding multiple silicon substrates 30 is provided. Underthe wafer stage 202, a heater 205 is provided for heating the siliconsubstrates 30 which is subjected to film deposition. The siliconsubstrate is heated by this heater 205 to a predetermined temperature.The wafer stage 202 is mechanically connected to a motor 206 via arotation shaft 207, and is capable of rotating at a predeterminedrotation speed in film deposition.

Moreover, a low-frequency power supply 204 is electrically connected tothe chamber 201 via a blocking capacitor 203, so that a low-frequencypower can be applied to a deposition atmosphere.

At a bottom portion of the chamber 201, an exhaust pipe 211 is provided.The exhaust pipe 211 is connected to an exhaust pump 210 via a butterflyvalve 209. A manometer 208 is provided to the exhaust pipe 211. Theopening degree of the butterfly valve 209 is adjusted based on an outputsignal from the manometer 208, to keep the inside of the chamber 201 ata predetermined pressure.

A plasma CVD can use a lower deposition temperature than a low-pressureCVD method and the like, and hence has an advantage that the capacitordielectric film 48 a is less likely to be deteriorated by heat.

In this embodiment, a silicon oxide film to serve as a third interlayerinsulating film 68 is formed on the third insulating hydrogen barrierfilm 66 by a plasma CVD method by supplying a gas mixture of TEOS gasand oxygen gas to the chamber 201 as a reaction gas. The film thicknessof the third interlayer insulating film 68 is approximately 2600 nm onthe first metal wirings 65 a, for example.

Deposition condition of the third interlayer insulating film 68 is notparticularly limited. In this embodiment, the frequency of thelow-frequency power to be applied to the chamber 201 by thelow-frequency power supply 204 is set at 250 Hz and the power is set at600 W. Here, in addition to the low-frequency power supply 204, anunillustrated high-frequency power supply may apply a high-frequencypower to the chamber 201. In this case, the frequency of thehigh-frequency power is set at 13.56 MHz, and the power is set at 400 W.Moreover, a heating temperature of the silicon substrates 30 by theheater 205 is set to 250° C. to 400° C., e.g., 350° C. The flow rates ofoxygen gas and TEOS gas are set at 800 sccm and 1800 sccm, respectively,and the pressure is set at approximately 2.2 Torr.

Even if the third interlayer insulating film 68 is deposited by theplasma CVD method in this manner, the protection film 64 prevents theupper surfaces of the first metal wirings 65 a from being directlyexposed to the plasma atmosphere used in the deposition. Accordingly,damage caused to the capacitor Q, electrically connected to the firstmetal wirings 65 a, by plasma can be reduced, and deterioration of thecapacitor Q during manufacture can be prevented.

Here, the protection film 64 is not formed on side surfaces of the firstmetal wirings 65 a. However, since the plasma damage is mainly caused tothe capacitor Q in a direction perpendicular to the upper surface of thesilicon substrate 30, the capacitor Q can be protected from the plasmadamages only by forming the protection film 64 on the upper surfaces ofthe first metal wirings 65 a as in this embodiment.

Moreover, in this embodiment, the third insulating hydrogen barrier film66 is formed in advance. This can prevent hydrogen contained in thedeposition atmosphere of the third interlayer insulating film 68 fromreaching the capacitor dielectric film 48 a, and can prevent adeterioration of ferroelectric characteristics of the capacitordielectric film 48 a due to reduction of the capacitor dielectric film48 a by hydrogen.

Moreover, the third insulating hydrogen barrier film 66 is formed on theside surfaces of the first metal wirings 65 a. This reduces plasmadamage which may be caused to the side surfaces, and further effectivelyprotects the ferroelectric capacitor Q from the plasma atmosphere.

Subsequently, the upper surface of the third interlayer insulating film68 is polished by a CMP to be planarized, and then an N₂O plasma processis performed on the surface of the third interlayer insulting film 68 ina CVD apparatus under the conditions of a substrate temperature ofapproximately 350° C. and a process time of approximately four minutes.By such an N₂O plasma process, the third interlayer insulating film 68is dehydrated, and the surface of the third interlayer insulating film68 is nitrided. Thereby, silicon oxide, which has a high affinity forwater, is prevented from absorbing moisture.

Next, as illustrated in FIG. 2T, a silicon oxide film to serve as asecond cap insulating film 69 is formed on the third interlayerinsulating film 68 by a plasma CVD method using TEOS gas, to have athickness of approximately 100 nm.

Micro scratches occurring due to contact with a pad of a CMP apparatusin the CMP are formed in the upper surface of the third interlayerinsulating film 68, and the second cap insulating film 69 functions tofill the micro scratches to planarize the upper surface.

Thereafter, an alumina film, having excellent blocking propertiesagainst reducing substances such as hydrogen and moisture, to serve as afourth insulating hydrogen barrier film 70 for protecting the capacitordielectric film 48 a from reducing substances is formed on the secondcap insulating film 69 to have a thickness of approximately 20 nm.

Moreover, a silicon oxide film to serve as a first cover insulating film71 is formed on the fourth insulating hydrogen barrier film 70 by aplasma CVD method using TEOS gas, to have a thickness of approximately100 nm.

An N₂O plasma process may be performed on the first cover insulatingfilm 71 in a CVD apparatus, for dehydration and prevention of moistureresorption of the first cover insulating film 71. The N₂O plasma processis performed under the conditions of a substrate temperature of 350° C.and a process time of two minutes, for example.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2U.

First, a photoresist is applied onto the first cover insulating film 71,and is then exposed and developed. Thereby, a fourth resist pattern 73including hole-shaped fourth windows 73 a over the first metal wirings65 a is formed.

Then, insulating films 66 and 68 to 71 under the fourth windows 73 a areetched by using a parallel-plate type plasma etching chamber (notillustrated) using gas mixture of C₄F₈, Ar, and O₂ as an etching gas.Thereby, fourth holes 74 a are formed respectively on the first metalwirings 65 a.

Here, if the third insulating hydrogen barrier film 66 to be etched istoo thick, formation of the fourth holes 74 a by etching is difficult.To facilitate the etching, the thickness of the third insulatinghydrogen barrier film 66 is preferably set to be 30 nm or thinner.

When using the above-described etching gas, the titanium nitride filmformed as the uppermost layer of the first metal wirings 65 a serves asa stopper of the etching. This prevents the fourth holes 74 a frompassing through the titanium nitride film, and thereby prevents thecopper-containing aluminum film constituting the first metal wirings 65a from being exposed from a bottom surface of the fourth hole 74 a.Thereby, it is possible to prevent an increase in contact resistancebetween a conductive plug, to be formed in the fourth holes 74 a later,and the first metal wiring 65 a due to aluminum.

Upon completion of the etching, the fourth resist pattern 73 is removed.

Then, as illustrated in FIG. 2V, a titanium nitride film to serve as afirst glue film 76 is formed on an inner surface of each of the fourthholes 74 a and an upper surface of the first cover insulating film 71 bya sputtering method by maintaining a substrate temperature atapproximately 200° C., to have a thickness of approximately 150 nm.

Subsequently, a tungsten film 77 a is formed on the first glue film 76by a plasma CVD method using tungsten hexafluoride gas, to have athickness enough to completely fill the fourth holes 74 a, e.g.,approximately 650 nm.

Then, as illustrated in FIG. 2W, the tungsten film 77 a is etched backto remove the tungsten film 77 a from the upper surface of the firstcover insulating film 71 while leaving the tungsten film 77 a only inthe fourth holes 74 a. Thereby, a second conductive plug 77 electricallyconnected to the first metal wiring 65 a and mainly made of tungsten isformed in each of the fourth holes 74 a.

Here, although the tungsten film is etched back in this example, CMP maybe employed instead of etch back.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 2X.

First, a metal laminated film is formed on the second conductive plugs77 and the first glue film 76 by a sputtering method. The metallaminated film contains, from its bottom, a copper-containing aluminumfilm having a thickness of approximately 550 nm, a titanium film havinga thickness of approximately 5 nm and a titanium nitride film having athickness of approximately 150 nm, in this order.

Thereafter, the metal laminated film and the first glue film 76 arepatterned by a photolithography. Thereby, second metal wirings 78 formedof these films are formed on the first cover insulating film 71.

In this patterning, the metal laminated film and the first glue film 76are over etched so as not to leave film residue on the first coverinsulating film 71.

Even when such an over-etching is performed, it is possible to preventthe fourth insulating hydrogen barrier film 70 from being etched in thepatterning and becoming thin, since the fourth insulating hydrogenbarrier film 70 is covered with the first cover insulating film 71.Accordingly, the fourth insulating hydrogen barrier film 70 can maintaina sufficient thickness even after the above patterning, and reducingsubstances such as hydrogen can be effectively blocked by the fourthinsulating hydrogen barrier film 70.

Subsequently, as illustrated in FIG. 2Y, a silicon oxide film to serveas a fourth interlayer insulating film 82 is formed on the first coverinsulating film 71 and the second metal wirings 78 by a plasma CVDmethod using a mixed gas of TEOS gas and oxygen gas, to have a thicknessof approximately 2200 nm.

Then, after an upper surface of the fourth interlayer insulating film 82is polished and planarized by a CMP method, an N₂O plasma process isperformed on the fourth interlayer insulating film under the conditionsof a substrate temperature of 350° C. and a process time of fourminutes. Thereby, the fourth interlayer insulating film 82 is dehydratedand a surface of the fourth interlayer insulating film 82 is nitrided.This prevents moisture resorption of the fourth interlayer insulatingfilm 82. The N₂O plasma process is performed by using a CVD apparatus,for example.

Thereafter, as illustrated in FIG. 2Z, a third cap insulating film 83, afifth insulating hydrogen barrier film 84 and a second cover insulatingfilm 85 are formed on the fourth interlayer insulating film 82, in thesame way as the formation of the insulating films 69 to 71.

Among the insulating films, the third cap insulating film 83 and thesecond cover insulating film 85 are each formed by a plasma CVD methodusing TEOS gas, to have a film thickness of approximately 100 nm. On theother hand, the fifth insulating hydrogen barrier film 84 is formed ofan alumina film having a thickness of approximately 50 nm formed by asputtering method.

Here, an N₂O plasma process may be performed on the third cap insulatingfilm 83 and the second cover insulating film 85 after their deposition,to dehydrate the insulating films. The N₂O plasma process is performedat a substrate temperature of 350° C. for two minutes, for example.

Thereafter, as illustrated in FIG. 3A, a photoresist is applied onto thesecond cover insulating film 85, and is then exposed and developed.Thereby, a fourth resist pattern 88 including hole-shaped fifth windows88 a over the second metal wirings 78 is formed.

Then, the insulating films 82 to 85 are etched in a parallel-plate typeplasma etching chamber by using the fourth resist pattern 88 as a mask.Thereby, a fifth hole 87 a is formed in portions, above each of thesecond metal wirings 78, of the insulating films. In this etching, gasmixture of C₄F₈, Ar, and O₂ is used as an etching gas, for example.

After the completion of the etching, the fourth resist pattern 88 isremoved.

Subsequently, as illustrated in FIG. 3B, a titanium nitride film toserve as a second glue film is formed on an inner surface of each of thefifth holes 87 a and an upper surface of the second cover film 85 by asputtering method, to have a thickness of approximately 50 nm. Then, atungsten film 91 a is formed on the second glue film 90 by a CVD methodto completely fill the fifth holes 87 a. The tungsten film 91 a isformed to have a thickness of approximately 650 nm, for example.

Thereafter, as illustrated in FIG. 3C, an excess tungsten film 91 a onthe second cover insulating film 85 is removed by etch back, to leavethe tungsten film 91 a as third conductive plugs 91 only in the fifthholes 87 a. Here, the tungsten film 91 a may be removed by a CMP methodinstead of etch back.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 3D.

First, a copper-containing aluminum film having a thickness ofapproximately 500 nm and a titanium nitride film having a thickness ofapproximately 150 nm are formed on the second glue film 90 and the thirdconductive plugs 91 in this order by a sputtering method. Then, themetal laminated film thus formed and the second glue film 90 under themetal laminated film are patterned by a photolithography, to form athird metal wiring 92 and a bonding pad 92 a respectively in the cellregion R_(cell) and the pad region R_(pad).

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 3E.

First, a silicon oxide film as an insulating film constituting a firstpassivation film 95 is formed on the second cover insulating film 85 andthe third metal wiring 92 by a CVD method, to have a thickness ofapproximately 100 nm.

Here, a N₂O plasma process for a dehydration process and a moistureabsorption prevention process may be performed on the first passivationfilm 95. The N₂O plasma process is performed, for example, in a CVDapparatus under the process conditions of a substrate temperature of350° C. and a process time of two minutes.

Moreover, a silicon nitride film to serve as a second passivation film96 is formed on the first passivation film 95 by a CVD method, to have athickness of approximately 350 nm.

Then, the first and second passivation films 95 and 96 are selectivelydry-etched to form a sixth hole 96 a, from which the bonding pad 92 a inthe pad region R_(pad) is exposed.

Thereafter, a photosensitive polyimide to serve as a protection layer 97made of a polyimide coating film is formed over the entire upper surfaceof the silicon substrate 30, to have a thickness of approximately 3 μm.Then, the protection layer 97 is exposed and developed, to form aseventh hole 97 a from which the bonding pad 92 a is exposed, in theprotection layer 97. Subsequently, the protection film 97 is thermosetunder the conditions of a substrate temperature of 310° C., a N₂ flowrate of 100 liter/min and a process time of 40 minutes.

Through the above steps, the basic structure of the semiconductor deviceaccording to this embodiment is completed.

According to the above-described embodiment, since the protection film64 is formed in advance on the first metal wirings 65 a, the first metalwirings 65 a are not directly exposed to the plasma atmosphere in thedeposition of the third interlayer insulating film 68 by the plasma CVDmethod. By causing the protection film 64 to function as a plasmaprotection film in this manner, deposition damage can be prevented fromreaching the capacitor dielectric film 48 a through the first metalwirings 65 a, so that the capacitor dielectric film 48 a can maintainhigh ferroelectric characteristics.

In particular, an insulating metal oxide film such as an alumina filmconstituting the protection film 64 has excellent barrier propertiesagainst hydrogen. Therefore, the protection film 64 also leads to suchan advantage that reduction and deterioration of the capacitordielectric film 48 a due to hydrogen can be prevented.

In addition, as illustrated in FIGS. 2P and 2Q, the metal laminated film65 is patterned to be made into the first metal wirings 65 a, in thestate where the protection film 64 is formed on the metal laminated film65. Accordingly, even if impurities such as water and hydrocarbon areremaining on the side surfaces of the first metal wirings 65 a in thewet process performed to remove a resist residue after the patterning,the adhesiveness between the protection film 64 and the metal laminatedfilm 65 is unlikely to be reduced due to the impurities.

For this reason, annealing for vaporizing the impurities does not needto be performed on the first metal wirings 65 a after the wet process.This can prevent deterioration of the ferroelectric characteristics ofthe capacitor dielectric film 48 a due to heat by annealing.

FIG. 4 is a graph obtained by actually investigating the residualpolarization charge of the capacitor dielectric film 48 a to verify theabove-described advantages.

In this investigation, the result obtained by using capacitors Qmanufactured by the method described on the basis of FIGS. 1A to 1G isprovided as a comparative example.

As to the present embodiment, the case of omitting the third insulatinghydrogen barrier film (embodiment 1) and the case of forming the thirdinsulating hydrogen barrier film 66 (embodiment 2) are investigated.

In each case, the graph depicts the average value of the residualpolarization charges of 1224 capacitors in a wafer surface.Additionally, variations (3σ) in residual polarization charge in thewafer surface are also depicted.

As depicted in FIG. 4, in the comparative example, the residualpolarization charge is decreased compared with the embodiments 1 and 2,and is only approximately 25.5 μC/cm². This is considered to be becausethe annealing for vaporizing impurities adhering to the wirings 23 isperformed as described on the basis of FIG. 1E, and thereby thecapacitor dielectric film 16 is deteriorated due to heat by theannealing.

On the other hand, in embodiments 1 and 2, a decrease in residualpolarization charge is prevented by omitting the annealing for the firstmetal wirings 65 a as described above, and hence a residual polarizationcharge which is higher by approximately 3% to 7% than that in thecomparative example can be obtained. Consequently, in the embodiments 1and 2, the operating margin of the semiconductor device includingferroelectric capacitors Q increases, and the yield of the semiconductordevice is improved.

Moreover, this investigation also reveals that a decrease in residualpolarization charge can be suppressed even when the third insulatinghydrogen barrier film 66 is omitted as in embodiment 1.

Nevertheless, a decrease in residual polarization charge can be moreeffectively prevented when the third insulating hydrogen barrier film 66is formed as in embodiment 2.

As described above, a decrease in residual polarization charge issuppressed in embodiments 1 and 2. Hence, it is not necessary to performannealing in an oxygen-containing atmosphere to increase the residualpolarization charge of the capacitor dielectric film 48 a after theformation of the first metal wirings 65 a. This prevents oxidation ofthe first metal wirings 65 a and the first conductive plugs 60 by theannealing, and thereby prevents an increase in contact resistancebetween the first metal wirings 65 a and the first conductive plugs 60.

Moreover, in this embodiment, the first metal wirings 65 a and thesecond interlayer insulating film 55 are covered by the third insulatinghydrogen barrier film 66. By the third insulating hydrogen barrier film66, plasma damage which may be caused to the side surfaces, on which theprotection film 64 is not formed, of the first metal wirings 65 a can bereduced. Thereby, deterioration of the capacitor can be suppressed moreeffectively when forming the third interlayer insulating film 68.

The third insulating hydrogen barrier film also has a function ofpreventing hydrogen ingress. Accordingly, the ferroelectric capacitors Qin the semiconductor device shipped as a product hardly deteriorate dueto hydrogen in an external atmosphere. Consequently, the long-termreliability of the ferroelectric capacitors Q is improved.

Here, it is conceivable that, when depositing the third interlayerinsulating film 68 by the plasma CVD method, the capacitor dielectricfilm 48 a deteriorates by an electric action of charged particlesincluded in the deposition atmosphere. In view of such possibility, itis preferable that an insulating film be formed as the protection film64 for isolating the first metal wirings 65 a from the plasmaatmosphere, so that the electric action of the charged particles wouldnot affect the capacitor dielectric film 48 a through the first metalwirings 65 a.

Description is given below of a preferable example of an insulating filmas the protection film 64.

First Example

In this example, a silicon oxide film is formed as the protection film64 by a sputtering method. A silicon oxide film can also protect thefirst metal wirings 65 a from plasma generated when forming the thirdinterlayer insulating film 68. Therefore, the protection film 64 canprevent damage from being caused to the capacitor dielectric film 48 athrough the first metal wirings 65 a.

Moreover, in a sputtering method, plasma is attracted to a sputteringtarget facing a substrate. Accordingly, deposition damage caused to thecapacitor dielectric film 48 a is smaller in a sputtering method than ina plasma CVD method. Hence, by forming the protection film 64 made ofsilicon oxide by a sputtering method, damage can be prevented from beingcaused to the capacitor Q when forming the protection film 64.

Here, the thickness of the protection film is not particularly limitedin this example, and is set between 2 nm and 30 nm, for example.

The minimum film thickness is set at 2 nm, because the function forprotecting the capacitor Q from the plasma atmosphere may decrease ifthe thickness is smaller than 2 nm. In addition, the maximum filmthickness is set at 30 nm, because it is difficult to etch theprotection film 64 in the step illustrated in FIG. 2Q if the thicknessis larger than 30 nm.

Second Example

In this example, a coat-type insulating film is formed as the protectionfilm 64. The coat-type insulating film is also called as a spin on glass(SOG).

Coating process does not require plasma when forming the protection film64, and thus is less harmful to a ferroelectric-capacitor-Q.

As the coat-type insulating film, a methylsiloxane based SOG such asAllied 211 available from RASA Industries, Ltd. can be formed.Alternatively, a phosphorus-doped silicon based SOG can be formed as theprotection film 64.

In the case of methylsiloxane-system SOG, a SOG coating film is formedon the metal laminated film 65 by a spin coat method, and is then bakedunder the conditions of a substrate temperature of 120° C. and a processtime of 90 seconds. Thereafter, the SOG coating film is cross-linked byheat under the conditions of a substrate temperature of 200° C. to 250°C. and a process time of 15 minutes, to form the protection film 64.Although hydrogen and moisture are generated from the SOG coating filmin the cross-linking, reduction and deterioration of the capacitordielectric film 48 a do not occur since the hydrogen and the like areblocked by the metal laminated film 65 that is already formed over theentire upper surface of the silicon substrate 30 (see FIG. 2O).

The film thickness of the protection film made of the coat-typeinsulating film is set between 10 nm to 30 nm, for example. The minimumfilm thickness is set at 10 nm, because a pinhole, which disables theprotection film 64 from protecting the capacitor Q from the plasmaatmosphere, is more likely to be produced in the protection film 64having thickness smaller than 10 nm. Moreover, the maximum filmthickness is set at 30 nm in consideration of difficulty of etching asin the case of first example.

Third Example

In this example, a resin film such as a polyimide film is formed as theprotection film 64. Any of a photosensitive polyimide film and anon-photosensitive polyimide film can be formed as the protection film64.

In the case of forming a non-photosensitive polyimide film, a polyimidecoating film is formed on the metal laminated film 65, and is thencross-linked in a nitrogen atmosphere under the conditions of asubstrate temperature of 180° C. to 220° C. and a process time of 20minutes. Thereby, the protection film 64 is formed.

As in the second example, alcohol, hydrogen, water and the like aregenerated in the cross-linking of the polyimide coating film. However,downward diffusion of these reducing substances is prevented by themetal laminated film 65, and hence the capacitor dielectric film 48 a isunlikely to be deteriorated by these reducing substances.

However, if the substrate temperature at the time of cross-linking istoo high or the cross-linking time is too long, the capacitor dielectricfilm 48 a may be deteriorated due to heat. For this reason, it ispreferable that the polyimide coating film be cross-linked under theconditions of the relatively low substrate temperature of 180° C. to250° C., and a process time of 15 minutes or shorter.

The thickness of the protection film 64 made of polyimide is preferablybetween 10 nm and 30 nm for the same reasons as in the second example.

To form a polyimide film having such a thin film thickness, it sufficesto dilute polyimide by solvent to lower concentration than in the caseof forming the protection layer 97 (see FIG. 3E), and apply thepolyimide whose viscosity is thus lowered. Although polyimide used hereis not limited to a particular kind, polyimide SP-811 from TORAYIndustries, Inc. can be used, for example.

Fourth Example

In this example, a ferroelectric oxide film is formed as the protectionfilm 64 by a sputtering method. A ferroelectric oxide film hascharacteristics of occluding hydrogen. Accordingly, the protection film64 made of a ferroelectric oxide film occludes hydrogen contained in anexternal atmosphere and hydrogen generated in manufacturing. Thus, theprotection film 64 prevents reduction and deterioration of the capacitorfilm 48 a due to hydrogen, and consequently contributes to improvementof the long-term reliability of the ferroelectric capacitor Q.

Examples of such a ferroelectric oxide film include a PZT.Alternatively, a PZT doped with a small amount of additive such aslanthanum and calcium (PLZT, for example) may be formed as theferroelectric oxide film. Moreover, a ferroelectric oxide film made of abismuth layer structured compound such as SBT or BLT may be formed asthe protection film 64.

Moreover, by forming a ferroelectric oxide film by a sputtering methodthat causes less damage due to plasma than in a plasma CVD method,damage can be prevented from being caused to the capacitor Q through themetal laminated film 65 when depositing the ferroelectric oxide film.

Although not particularly limited, the thickness of the protection film64 made of ferroelectric oxide is set between 2 nm to 10 nm, forexample. The reasons why the minimum and maximum film thicknesses arethus set are the same as those in the first example.

It is to be noted that the etching of the protection film 64 in FIG. 2Qcan be performed by using the same etching gas as that used in thisembodiment described above, in any cases of forming the insulating filmsof the above-described first to fourth examples as the protection film64.

Second Embodiment

Next, description is given of a second embodiment.

In this embodiment, the first embodiment described above is applied to astack-type FeRAM.

FIGS. 6A to 6V are cross-sectional views of a semiconductor deviceaccording to this embodiment in the course of manufacturing. In thedrawings, the same elements as those described in the first embodimentare denoted by the same numerals, and description thereof is omitted inthe following.

Firstly, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 6A.

First, after the steps illustrated in FIGS. 2A and 2B in the firstembodiment, the base insulating film 44 and the first interlayerinsulating film 45 are patterned, and thereby first holes 45 a areformed in the insulating films. Then, a titanium film and a titaniumnitride film to serve as a glue film are formed in this order in thefirst holes 45 a and on the first interlayer insulating film 45. Thetitanium film and the titanium nitride films are formed by a sputteringmethod to have a thickness of approximately 20 nm and a thickness ofapproximately 50 nm, respectively.

Moreover, a tungsten film is formed on the glue film by a CVD method tocompletely fill the first holes 45 a. Thereafter, an excess of the gluefilm and the tungsten film on the first interlayer insulating film 45 ispolished by a CMP method and removed. Thereby, the films are left asfirst conductive plugs 100 only inside the first holes 45 a.

Subsequently, the first interlayer insulating film 45 is exposed to N₂Oplasma. Thereby, the first interlayer insulating film 45 is dehydratedand a surface of the first interlayer insulating film 45 is nitrided toprevent moisture resorption. Conditions for the N₂O plasma process arenot particularly limited. In this embodiment, the process is performedfor two minutes under the condition of a substrate temperature of 350°C.

Then, as illustrated in FIG. 6B, a silicon oxy-nitride film to serve asa first oxidation prevention insulating film 102 for preventingoxidation of the first conductive plugs 100 is formed by a CVD method tohave a thickness of approximately 100 nm.

Alternatively, instead of a silicon oxy-nitride film, a silicon nitridefilm may be formed as the first oxidation prevention insulating film102.

Moreover, to increase the adhesiveness between the first oxidationprevention insulating film 102 and capacitor lower electrodes to bedescribed later, a silicon oxide film to serve as an insulating adhesivefilm 103 is formed on the first oxidation prevention insulating film 102to have a thickness of approximately 100 nm.

Subsequently, as illustrated in FIG. 6C, the insulating films 102 and103 are patterned to form a second hole 103 a in portions, above eachfirst source/drain region 39 a, of the insulating films. Then, a secondconductive plug 104 is formed in the second hole 103 a.

The second conductive plug 104 is formed by forming a glue film and atungsten film in this order, and is formed by the same method as thatfor the first conductive plugs 100, the glue film being formed of alaminated film including a titanium film and a titanium nitride film.

Thereafter, an N₂O plasma process is performed on the insulatingadhesive film 103 under the conditions of a substrate temperature of350° C. and a process time of two minutes, for dehydration andprevention of moisture resorption of the insulating adhesive film 103.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 6D.

First, a titanium film 105 x is formed on the insulating adhesive film103 by a sputtering method to have a thickness of approximately 20 nm.The titanium film 105 x functions to make the orientation of aferroelectric film to be formed thereabove uniform, by its orientation.

Then, a titanium aluminum nitride (TiAlN) film 105 y having a thicknessof approximately 100 nm and an iridium oxide film 105 z having athickness of approximately 100 nm are formed on the titanium film 105 xin this order by a sputtering method. Thereby, a first conductive film105 is formed of the films 105 x to 105 z.

Even if oxygen permeates through the iridium oxide film 105 z inrecovery annealing in an oxygen-containing atmosphere to be describedlater, the oxygen can be blocked by the titanium aluminum nitride film105 y formed in the first conductive film 105 as described above. Thus,it is possible to prevent oxidation and contact failure of the secondconductive plugs 104. Additionally, the titanium aluminum nitride film105 y has conductivity even if being oxidized, and is thereforepreferable as a film for blocking oxygen on the plugs 104.

Thereafter, a PZT film to serve as a ferroelectric film 106 is formed onthe first conductive film 105 by a MOCVD method to have a thickness ofapproximately 120 nm.

Then, a first iridium oxide film is formed on the ferroelectric film 106by a sputtering method to have a thickness of approximately 50 nm, andthen RTA is performed on the first iridium oxide film in anoxygen-containing atmosphere. The RTA is performed under the conditionsof a substrate temperature of 725° C. and a process time of 60 seconds,for example. Moreover, oxygen gas of 0.025 litter/min is supplied to theannealing atmosphere.

Subsequently, a second iridium oxide film is formed on the first iridiumoxide film by a sputtering method to have a thickness of approximately100 nm. Thus, a second conductive film 107 formed of the laminated filmincluding the first and second iridium oxide films is formed.

RTA is performed on the second conductive film 107 in anoxygen-containing atmosphere under the conditions of a substratetemperature of 700° C., an oxygen flow rate of 0.025 liter/min and aprocess time of 60 seconds.

Then, as illustrated in FIG. 6E, a titanium nitride film to serve as afirst mask material layer 108 is formed on the second conductive film107 by a sputtering method to have a thickness of approximately 200 nm.

Moreover, a silicon oxide film to serve as a second mask material layer109 is formed on the first mask material layer 108 by a CVD method usingTEOS gas, to have a thickness of approximately 700 nm.

Thereafter, as illustrated in FIG. 6F, a first resist pattern 110 havingcapacitor planar shapes is formed on the second mask material layer 109.

Then, as illustrated in FIG. 6G, the second mask material layer 109 isetched by using the first resist pattern 110 as a mask, to thereby forma second hard mask 109 a.

Moreover, as illustrated in FIG. 6H, the first mask material layer 108is etched by using the second hard mask 109 a as a mask, to thereby forma first hard mask 108 a. The first resist pattern 110 is reduced in filmthickness by being exposed to the etching atmosphere, and mostlydisappears by the time when the etching is completed.

Subsequently, as illustrated in FIG. 6I, the first conductive film 105,the ferroelectric film 106 and the second conductive film 107 are etchedall at once by using the first and second hard masks 108 a and 109 a asmasks. Thereby, capacitors Q each having the lower electrode 105 a, thecapacitor dielectric film 106 a and the upper electrode 107 a stacked inthis order are formed as illustrated in FIG. 6I.

The lower electrode 105 a forming the capacitor Q is directly connectedto a corresponding one of the second conductive plugs 104, and iselectrically connected to a corresponding one of the first source/drainregions 39 a through the first conductive plug 100 under the secondconductive plug 104.

In addition, the plugs in two levels, i.e., the first and secondconductive plugs 100 and 104, are provided immediately under thecapacitor Q, and the holes 45 a and 103 a in which the plugs areembedded respectively are formed individually. This reduces the aspectratio of each of the holes, thereby facilitating formation of the holes.

Then, the first and second hard masks 108 a and 109 a are removed by dryetching and wet etching.

Then, to recover damage caused to the capacitor dielectric film 106 a inthe above-described steps, recovery annealing is performed on thecapacitor dielectric film 106 a in a vertical furnace having anoxygen-containing atmosphere. The conditions for the recovery annealingare not particularly limited. In this embodiment, the annealing isperformed under the conditions of a substrate temperature of 350° C., anoxygen flow rate of 20 litter/min and a process time of 40 minutes.

Next, description is given of steps for obtaining a cross-sectionalstructure illustrated in FIG. 6J.

First, to protect the capacitor dielectric film 106 a from reducingsubstances such as moisture and hydrogen, an alumina film to serve as afirst insulating hydrogen barrier film 110 is formed over the entireupper surface of the silicon substrate 30 by an atomic layer deposition(ALD) method, to have a thickness of approximately 50 nm. An aluminafilm is excellent in blocking the reducing substances.

Then, a silicon oxide film to serve as a second interlayer insulatingfilm 111 is formed on the first insulating hydrogen barrier film 110 tohave a thickness of approximately 1500 nm. The silicon oxide film fillsa narrow gap between two adjacent capacitors Q, and is hence preferablyformed by a high density plasma CVD (HDPCVD) method, which providesexcellent gap-filling properties.

Thereafter, an upper surface of the second interlayer insulating film111 is polished by a CMP method and planarized, and then an alumina filmto serve as a second insulating hydrogen barrier film 112 for protectingthe capacitor dielectric film 106 a from reducing substances is formedby an ALD method to have a thickness of approximately 50 nm.

Furthermore, a silicon oxide film to serve as a buffer insulating film113 is formed on the second insulating hydrogen barrier film 112 to havea thickness of approximately 100 nm. The silicon oxide film can beformed by a CVD method using TEOS gas.

Then, as illustrated in FIG. 6K, a photoresist is applied on the bufferinsulating film 113, and is then exposed and developed. Thereby, asecond resist pattern 115 is formed.

Subsequently, the insulating films from the buffer insulating film 113to the first oxidation prevention insulating film 102 are etched byusing the second resist pattern 115 as a mask. Thereby, a third hole 117is formed in portions, above each of the first conductive plugs 100, ofthe insulating films.

Thereafter, the second resist pattern 115 is removed.

Then, as illustrated in FIG. 6L, a titanium film having a thickness ofapproximately 20 nm and a titanium nitride film having a thickness ofapproximately 50 nm to serve as a glue film are formed in this order inthe third holes 117 and on the buffer insulating film 113 by asputtering method. Further, a tungsten film is formed on the glue filmby a CVD method to completely fill the third holes 117. Then, an excessof the glue film and the tungsten film on the buffer insulating film 113is polished by a CMP method and removed, to leave the films as thirdconductive plugs 118 only inside the third holes 117. The thirdconductive plugs 118 are each directly connected to the first conductiveplug 100 thereunder.

The third conductive plugs 118 are mainly made of tungsten, which iseasily oxidized, and are hence likely to be oxidized in the course ofmanufacturing the semiconductor device and consequently have contactfailure.

In view of this, as illustrated in FIG. 6M, in the next step, a siliconoxy-nitride film to serve as a second oxidation prevention insulatingfilm 120 is formed on the third conductive plugs 118 and the bufferinsulating film 113 by a CVD method to have a thickness of approximately100 nm. Thereby, the second oxidation prevention insulating film 120protects the third conductive plugs 118 from an oxygen-containingatmosphere.

Subsequently, as illustrated in FIG. 6N, the insulating films 110 to 113and 120 are patterned. Thereby, a fourth hole 122 is formed in portions,above each of the upper electrodes 107 a, of the insulating films.

Then, to recover damage caused to the capacitor dielectric film 106 a inthe above-described steps, recovery annealing is performed on thecapacitor dielectric film 106 a in an oxygen-containing atmosphere in avertical furnace.

The recovery annealing is performed under the conditions of a substratetemperature of 500° C., an oxygen gas flow rate of 20 liter/min and aprocess time of 60 minutes, for example.

Even if the annealing is performed in an oxygen-containing atmosphere,oxidation and contact failure of the third conductive plugs 118, mainlymade of tungsten, are prevented since the third conductive lugs 118 areprotected by the second oxidation prevention insulating film 120.

After the recovery annealing is completed, the second oxidationprevention insulating film 120 is etched and removed.

Then, as illustrated in FIG. 6O, a fourth conductive plug 127 is formedin each of the fourth holes 122 to be electrically connected to thecorresponding upper electrode 107 a.

To form such fourth conductive plugs 127, a titanium nitride film toserve as a glue film is formed inside the fourth holes 122 and on thebuffer insulating film 113 by a sputtering method, and a tungsten filmis formed on the glue film by a CVD method, to completely fill thefourth holes 122 with the tungsten film. Then, an excess of the gluefilm and the tungsten film on the buffer insulating film 113 is polishedby a CMP method and removed. Thereby, the fourth conductive plugs 127formed of these films can be formed in the fourth holes 122.

Subsequently, as illustrated in FIG. 6P, a metal laminated film 130 isformed on the third and fourth conductive plugs 118 and 127 and thebuffer insulating film 113 by a sputtering method. The metal laminatedfilm 130 is formed of a copper-containing aluminum film having athickness of approximately 550 nm, a titanium film having a thickness ofapproximately 5 nm and a titanium nitride film having a thickness ofapproximately 150 nm in this order from the bottom.

Then, as illustrated in FIG. 6Q, an alumina film to serve as aprotection film 131 for protecting the metal laminated film 130 and thecapacitor dielectric film 106 from a plasma atmosphere is formed on themetal laminated film 130 by a sputtering method to have a thickness ofapproximately 20 nm.

The protection film 131 is not limited to an alumina film. Instead of analumina film, an insulating metal oxide film such as a titanium oxidefilm, a zirconium oxide film, a magnesium oxide film or a titaniummagnesium oxide film may be formed as the protection film 131.

Still alternatively, any one of the insulating films described in thefirst to fourth examples of the first embodiment may be formed as theprotection film 131. Such insulating films include a silicon oxide filmformed by a sputtering method (first example), a coat-type insulatingfilm (second example), a resin film (third example) and ferroelectricoxide film (fourth example).

Thereafter, as illustrated in FIG. 6R, a photoresist is applied onto theprotection film 131, and is then exposed and developed. Thereby, a thirdresist pattern 132 is formed.

Then, as illustrated in FIG. 6S, the protection film 131 and the metallaminated film 130 are dry-etched by using the third resist pattern 132as a mask. Thereby, the metal laminated film 130 is made into firstmetal wirings 130 a.

The dry etching for the protection film 131 is performed in aparallel-plate type etching apparatus by using gas mixture of C₄F₈, Ar,and O₂ as an etching gas. In this case, the flow rates of C₄F₈ gas, Argas and O₂ gas are 20 sccm, 500 sccm and 12 sccm, respectively, forexample. Additionally, CF₄, CHF₃ or CO may be mixed into any of thegases.

Meanwhile, the dry etching for the metal laminated film 130 is performedin an ECR etching apparatus by using gas mixture of BCl₃ and Cl₂ as anetching gas. The flow rates of BCl₃ gas and Cl₂ gas are 105 sccm and 45sccm, respectively, for example.

After the etching is completed, the third resist pattern 132 is removedby asking, and a resist residue is removed by a wet process usingchemicals and pure water.

In the wet process, impurities such as moisture and hydrocarbon adhereto side surfaces of the first metal wirings 130 a. However, theadhesiveness of the protection film 131 already formed on the firstmetal wirings 130 a does not decrease due to the impurities.

Accordingly, annealing for vaporizing the impurities does not need to beperformed on the first metal wirings 130 a. This prevents deteriorationof the capacitor dielectric film 106 a due to heat by annealing.

Thereafter, as illustrated in FIG. 6T, an alumina film to serve as athird insulating hydrogen barrier film 133 for covering the first metalwirings 130 a and the buffer insulating film 113 is formed by asputtering method to have a thickness of 5 nm to 30 nm, e.g., 20 nm.

The third insulating hydrogen barrier film 133 functions to protect thecapacitor dielectric film 48 a by blocking reducing materials such ashydrogen and moisture, and may be formed of any insulating metal oxidefilm among a titanium oxide film, a zirconium oxide film, a magnesiumoxide film and a titanium magnesium oxide film, instead of an aluminafilm.

Alternatively, a silicon-containing insulating film containing nitrogensuch as a silicon nitride film or a silicon oxy-nitride film may beformed as the third insulating hydrogen barrier film 133.

Then, as illustrated in FIG. 6U, a silicon oxide film to serve as athird interlayer insulating film 135 is formed on the third insulatinghydrogen barrier film 133 by a plasma CVD method using a mixed gas ofTEOS gas and oxygen gas as a reactant gas, to completely fill gapsbetween the first metal wirings 130 a.

The third interlayer insulating film 135 may be deposited by a plasmaCVD method by using, for example, the plasma CVD apparatus 200 describedon the basis of FIG. 5.

Even though a plasma CVD method is employed, upper surfaces of the firstmetal wirings 130 a are covered by the protection film 131, whichfunctions as a plasma protection film. Accordingly, it is possible toreduce a possibility that damage caused in deposition due to plasmareaches the capacitor dielectric film 106 a through the first metalwirings 130 a, and to maintain excellent ferroelectric characteristicsof the capacitor dielectric film 106 a.

Thereafter, an upper surface of the third interlayer insulating film 135is polished by a CMP method and planaraized.

Then, an N₂O plasma process is performed on a surface of the thirdinterlayer insulating film 135 in a CVD apparatus, to dehydrate thethird interlayer insulating film 135 and prevent moisture resorption bynitriding the surface. The N₂O plasma process is performed in a CVDapparatus under the conditions of a substrate temperature ofapproximately 350° C. and a process time of approximately four minutes.

After the above-described steps, a base structure of the semiconductordevice according to this embodiment is completed as illustrated in FIG.6V, by performing the steps described in FIGS. 2T to 2Z and 3A to 3E ofthe first embodiment.

According to the above-described embodiment, the protection film 131prevents the first metal wirings 130 a from being exposed to the plasmaatmosphere when depositing the third interlayer insulating film 135 asdescribed with reference to FIG. 6U. Accordingly, as in the firstembodiment, plasma damage is less likely to be caused to the capacitorsQ electrically connected to the first metal wirings 130 a. This reducesdamage caused to the capacitor dielectric film 106 a when forming thethird interlayer insulating film 135 by a plasma CVD method, andprevents deterioration of the ferroelectric characteristics of thecapacitor dielectric film 106 a.

Moreover, as illustrated in FIG. 6R, the protection film 131 is formedbefore the metal laminated film 130 is subjected to patterning.Accordingly, even if impurities such as moisture and hydrocarbon adhereto the side surfaces of the first metal wirings 130 a in the wet processperformed after the patterning of the metal laminated film 130, theadhesiveness between the first metal wirings 130 a and the protectionfilm 131 does not decrease due to the impurities. Consequently,annealing for vaporizing the impurities adhering to the first metalwirings 130 a can be omitted, which prevents deterioration of thecapacitor dielectric film 106 a due to heat by annealing.

Furthermore, the third insulating hydrogen barrier film 133 is formed onthe protection film 131, and can thereby prevent hydrogen contained inthe atmosphere used when depositing the third interlayer insulating film135 from reaching the capacitor dielectric film 106 a. This preventsreduction of the capacitor dielectric film 106 a due to hydrogen, andsuppresses a degradation of the capacitor dielectric film 106 a inferroelectric characteristics.

While this embodiment has been described in detail above, the presentinvention is not limited to the above-described embodiment. Although thesemiconductor substrate W having the orientation flat OF formed thereinis used in the above-described embodiment, the semiconductor substrate Whaving a notch formed therein instead of the orientation flat OF may beused, for example.

1. A semiconductor device comprising: a semiconductor substrateincluding a transistor; a first interlayer insulating film formed overthe semiconductor substrate and the transistor; a ferroelectriccapacitor formed over the first interlayer insulating film; a secondinterlayer insulating film formed over the first interlayer insulatingfilm and the ferroelectric capacitor; a wiring formed over the secondinterlayer insulating film; and a protection film formed over an uppersurface of the wiring but not on a side surface of the wiring.
 2. Thesemiconductor device according to claim 1, further comprising: a thirdinterlayer insulating film formed on the second interlayer insulatingfilm and the protection film, the third interlayer insulating film beingformed by a deposition method using plasma.
 3. The semiconductor deviceaccording to claim 2, wherein the protection film is a plasma protectionfilm for protecting the wiring from damage caused by plasma used forforming the third interlayer insulating film.
 4. The semiconductordevice according to claim 3, wherein the second interlayer insulatingfilm includes a hole formed at a portion over any one of a lowerelectrode and an upper electrode constituting the capacitor, and thewiring is electrically connected to the any one of the lower electrodeand the upper electrode through the hole.
 5. The semiconductor deviceaccording to claim 3, wherein the protection film is an insulating film.6. The semiconductor device according to claim 5, wherein the insulatingfilm is either any one of a silicon oxide film and a ferroelectric oxidefilm formed by a sputtering method, or any one of a coat-type insulatingfilm and a resin film.
 7. The semiconductor device according to claim 2,wherein the deposition method using plasma is a plasma CVD method. 8.The semiconductor device according to claim 1, wherein an insulatinghydrogen barrier film is formed over the protection film, the secondinterlayer insulating film, and on the side surface of the wiring. 9.The semiconductor device according to claim 8, wherein the insulatinghydrogen barrier film is formed of any one of an insulating metal oxidefilm and a silicon-containing insulating film containing nitrogen.
 10. Amethod of manufacturing a semiconductor device, comprising: forming atransistor on a semiconductor substrate; forming a first interlayerinsulating film over the semiconductor substrate and the transistor;forming a ferroelectric capacitor over the first interlayer insulatingfilm; forming a second interlayer insulating film over the firstinterlayer insulating film and the ferroelectric capacitor; forming awiring over the second interlayer insulating film; and forming aprotection film over an upper surface of the wiring but not on a sidesurface of the wiring.
 11. The method of manufacturing a semiconductordevice according to claim 10, wherein the formation of the wiringincludes: forming a conductive film over the second interlayerinsulating film; forming the protection film over the conductive film;forming a resist pattern over the protection film; etching theconductive film and the protection film by using the resist pattern as amask, to thereby make the conductive film into the wiring and leave theprotection film only over the upper surface of the wiring; and removingthe resist pattern.
 12. The method of manufacturing a semiconductordevice according to claim 11, wherein no annealing is performed on thewiring after forming the resist pattern and before forming a next filmover the second interlayer insulating film.
 13. The method ofmanufacturing a semiconductor device according to claim 10, wherein theprotection film is formed by any one of a sputtering method and adeposition method not using plasma.
 14. The method of manufacturing asemiconductor device according to claim 10, further comprising: forminga third interlayer insulating film over the second interlayer insulatingfilm, the wiring and the protection film by a deposition method usingplasma.
 15. The method of manufacturing a semiconductor device accordingto claim 14, wherein a plasma protection film for protecting the wiringfrom damage caused by plasma used in depositing the third interlayerinsulating film is formed as the protection film.
 16. The method ofmanufacturing a semiconductor device according to claim 15, wherein aninsulating film is formed as the protection film.
 17. The method ofmanufacturing a semiconductor device according to claim 16, whereineither any one of a silicon oxide film and a ferroelectric oxide film isformed by a sputtering method as the insulating film, or any one of acoat-type insulating film and a resin film is formed as the insulatingfilm.
 18. The method of manufacturing a semiconductor device accordingto claim 15, further comprising: forming a hole in the second interlayerinsulating film at a portion over any one of a lower electrode and anupper electrode constituting the capacitor, wherein the wiring iselectrically connected to the any one of the lower electrode and theupper electrode through the hole.
 19. The method of manufacturing asemiconductor device according to claim 10, further comprising: formingan insulating hydrogen barrier film over the protection film, the secondinterlayer insulating film, and on the side surface of the wiring. 20.The method of manufacturing a semiconductor device according to claim19, wherein any one of an insulating metal oxide film and asilicon-containing insulating film containing nitrogen is formed as theinsulating hydrogen barrier film.